Collecting baseball cards is a cherished pastime. ESPN baseball writer Sam Miller first got hooked on the game by studying the backs of cards growing up. And when he learned about a Don Mattingly card with a curious factoid on Mattingly's alleged birth year, Miller began a quest to uncover the truth. When was the former Yankees star first baseman born? And did this one baseball card have the inside scoop, or a crucial error? Miller tells us how he solved the mystery of Mattingly's real birth date.